Many types of immunoassays involve the interaction of a liquid sample with a solid material, and a determination of whether or not a reaction has taken place between species in the sample and species immobilized on the solid surface. The immobilization may be achieved either by covalent chemical bond or nonspecific binding such as electrostatic attraction, hydrophobic interaction or hydrogen bonding.
Handling of the solid phase by the operator is frequently a delicate procedure. In some cases, the membrane is thin and fragile. The membrane can be contaminated by inadvertent touching to the extent that its accuracy and reproducibility may be impaired. In addition, the species immobilized on the membrane may contain infectious material raising a safety hazard to those handling the membrane.
Drawing liquid through the solid phase is also problematic in some cases. Absorbent pads have been used on the downstream side of the membrane, but this requires very close contact between the membrane and the absorbent pad. Otherwise, bubbles form which obstruct the flow.
The present invention provides a canister for the support of a flow-through solid phase, which protects the solid phase and any species immobilized on it from inadvertent contact by the operator or other equipment, and permits flow across the solid phase solely by the force of gravity, retaining all liquids for proper disposal. The canister is comprised of two parts, an open-top receptacle and a cap for the receptacle, the cap designed to support the solid phase material. The cap has a central opening surrounded by a raised surface. The solid phase material spans the opening, and the raised surface serves as a protective wall encircling the material. The cap and receptacle are shaped to fit snugly and securely together and yet leave a gap to vent the interior of the receptacle to the atmosphere.